[beta] rustdoc: Stop unconditionally evaluating the initializer of associated consts

[fmease]

Last minute beta backport of #151232 (beta backport accepted).
Directly fixes #149635.

Not part of some hypothetical future backport rollup because we're under time pressure as the release procedures have commenced already: https://forge.rust-lang.org/#current-release-versions, https://forge.rust-lang.org/release/process.html.

r? fmease

[fmease]

https://forge.rust-lang.org/release/backporting.html#beta-backporting-in-rust-langrust

@bors rollup=never

https://forge.rust-lang.org/compiler/reviews.html#priority

@bors p=10

[fmease]

https://forge.rust-lang.org/release/backporting.html

Only a few people are even aware of the process, but this is actually something anybody can do.

A reviewer (typically from the release team) needs to verify that the backport looks correct and that it’s submitted to the beta branch. […]. If the author of the PR has r+ rights, and has not made significant changes while backporting, they can also self-approve the PR.

cc @cuviper for visibility (#149635 (comment))

Change the milestone to the correct value for the beta release.
Remove the beta-nominated label. This indicates that the backport has been completed.

Applied.

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@bors r+

[rust-bors]

📌 Commit 36e6625 has been approved by fmease

It is now in the queue for this repository.

[rust-bors]

☀️ Test successful - CI
Approved by: fmease
Pushing 9a4aba1 to beta...